口蹄疫病毒株China/99 P3区一级结构及与参考毒株的比较分析

用RT－PCR法，以口蹄疫病毒China/99感染的牛舌水泡皮为材料，扩增目的cDNA，与pGEM-T Easy载体连接并转化JM109菌株，再经重组质粒电泳、PCR和EcoR1酶切鉴定。序列测定和分析结果表明，猪源毒在3A基因内缺失10个密码子，与牛源毒的核苷酸和氨基酸序列差异较大。A－G和T－C的转换率较高，而且A－G转换导致氨基酸变异的几率大于T－C转换，它们是影响氨基酸稳定的因素之一。China/99P3区编码产物在第8、120、121、127、132、193、493、501和538位具有特征性氨基酸，可能与该毒株的表型如毒力等有关。3A基因突变率较高，3B、3C和3D较低，3D最为保守，这对维持3C和3D蛋白酶和3B的引物功能至关重要。

The Basic Structure of P3 Region from FMDV Strain China/99 and Comparison with Reference Strain's

The sequence of P3 region of a virulent foot and mouth disease virus strain China/99 RNA from infected bovine tongue epithelium was determined by cloning of cDNA fragments obtained from RT PCR.The cDNA fragments were inserted in pGEM T Vectors and transformed into JM109,then the recombinant plasmids were identified by electrophoresis,EcoR1 cleavage and PCR.The nucleotide and amino acid sequence of FMDV strain China/99 P3 region was compared with other six reference strain's.It was shown that the differential ratio of China/99 with A12,A10 61,twcp/97 and twty/97 were 8 48%,9 02%,7 89%,2 67%,13 87%,13 80%,respectively and that of amino acid sequences was 4 52%,4 62%,3 74%,2 75%,7 82%,7 38%,respectively.The sequence alignment of these strains showed that the differential ratio of the nucleotide and amino acid sequences was remarkable between the viruses that isolated from cattle and the viruses that came from swine,we speculated that the event might relate with the species of animals.The higher conversions in T C and A C that are hot nucleotides mostly affect the stable of amino acid residues.The mutant rate of 3A gene was highest in four genes others,and 3D gene was most conservative in these genes.The product encoded by China/99 P3 region had characteristics at 8th,120th,121th,127th,132th,193th,493th,501th and 538th,the sites above waredistinct different from others',might be related with the characteristics of the strain China/99,such as virulent.etc.